A chemical liquid, such as a photoresist liquid, spin on glass liquid, polyimide resin liquid, pure water, etching liquid, organic solvent, and the like, has been used in manufacturing processes in various technical fields such as techniques of manufacturing a liquid crystal board, a magnetic disk, a multi-layered wiring board, and the like, starting from a semiconductor wafer manufacturing technique. A chemical liquid supply apparatus has been used in coating such chemical liquid.
For example, in case of coating the photoresist liquid onto the surface of the semiconductor wafer, the predetermined amount of photoresist liquid is dropped onto the surface of the semiconductor wafer from the chemical liquid supply apparatus, after having rotated the semiconductor wafer in a horizontal plane.
If bubbles are mixed into the apparatus in discharging the chemical liquid such as a photoresist liquid, the bubbles absorb a pressure trying to push out the chemical liquid and thereby a discharge amount of chemical liquid becomes unstable and accuracy of the discharge is reduced. Due to this, a semiconductor integrated circuit to be formed onto the semiconductor wafer has been difficult to manufacture with high quality and good yield.
A filter is provided in such chemical liquid supply apparatus in order to capture the bubbles in the chemical liquid, and foreign matters such as bubbles or the like are removed by getting the chemical liquid passing through the filter to enhance an extent of cleanliness of the chemical liquid. The bubbles accumulated in a filter vessel has ordinarily been exhausted to the outside by opening a deaeration valve, which is provided in an exhaust flow path connected to an exhaust port of the filter.
However, since the bubbles gradually adhere to the surface of the filter and the clogging thereof occurs, the capability of capturing the bubbles is reduced gradually. Due to this, the filter cannot completely capture the bubbles in the chemical liquid, and the chemical liquid containing the bubbles is often discharged on the surface of the semiconductor wafer. Consequently, it has been difficult to improve the yield of manufacturing the semiconductor integrated circuit.
Thus, a conventional method, in which the bubbles are removed through the filter and exhausted from the filter, has its limitations. To solve the problems as described above, it is necessary, even at a place or places other than the filter in the supply apparatus, to properly remove the bubbles included in the chemical liquid and exhaust them outside the supply apparatus.
An object of the present invention is to make stable an amount of chemical liquid discharged from a chemical liquid supply apparatus and to improve the accuracy of the discharge.
Another object of the present invention is to manufacture the semiconductor integrated circuits with high quality and good yield.